Juergen Freund / Ancient pictographs (rock / cave paintings) of fish and sea creatures on karst limestone formations. Sunmalelen area, Raja Ampat, West Papua, Indonesia, January 2010

Vincent Grafhorst / Bushman rock paintings in the Drakensberg Mountains, Giant's Castle Nature Reserve, South Africa

Vincent Grafhorst / Bushman rock paintings in the Drakensberg Mountains, Giant's Castle Nature Reserve, South Africa

Jim Brandenburg / Pictographs, Lac La Croix, Boundary Waters Canoe Area Wilderness, Minnesota

Matthias Breiter / Aboriginal rock paintings at Nganalam Art Site, Keep River National Park, Australia

Richard Du Toit / Bushman rock art, fallen rock site, Bushman Kloof, Cederberg, South Africa

Mark Moffett / Green Tree Ant (Oecophylla smaragdina) group with rock art in the background, Kakadu National Park, Northern Territory, Australia

Jim Brandenburg / Cave art depicting hunters, Namibia

Jim Brandenburg / Pictograph of antelope, Namibia

Jim Brandenburg / Native American pictographs, Minnesota